diff --git a/spring-test/src/main/java/org/springframework/mock/web/MockHttpServletResponse.java b/spring-test/src/main/java/org/springframework/mock/web/MockHttpServletResponse.java
index 7e22d70d4fb..6bde5487b89 100644
--- a/spring-test/src/main/java/org/springframework/mock/web/MockHttpServletResponse.java
+++ b/spring-test/src/main/java/org/springframework/mock/web/MockHttpServletResponse.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -193,7 +193,8 @@ public class MockHttpServletResponse implements HttpServletResponse {
 		Assert.state(this.writerAccessAllowed, "Writer access not allowed");
 		if (this.writer == null) {
 			Writer targetWriter = (this.characterEncoding != null ?
-					new OutputStreamWriter(this.content, this.characterEncoding) : new OutputStreamWriter(this.content));
+					new OutputStreamWriter(this.content, this.characterEncoding) :
+					new OutputStreamWriter(this.content));
 			this.writer = new ResponsePrintWriter(targetWriter);
 		}
 		return this.writer;
diff --git a/spring-web/src/test/java/org/springframework/mock/web/test/MockHttpServletResponse.java b/spring-web/src/test/java/org/springframework/mock/web/test/MockHttpServletResponse.java
index 7f248e90931..d9f3488d0a8 100644
--- a/spring-web/src/test/java/org/springframework/mock/web/test/MockHttpServletResponse.java
+++ b/spring-web/src/test/java/org/springframework/mock/web/test/MockHttpServletResponse.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -168,11 +168,11 @@ public class MockHttpServletResponse implements HttpServletResponse {
 
 	private void updateContentTypeHeader() {
 		if (this.contentType != null) {
-			StringBuilder sb = new StringBuilder(this.contentType);
-			if (!this.contentType.toLowerCase().contains(CHARSET_PREFIX) && this.charset) {
-				sb.append(";").append(CHARSET_PREFIX).append(this.characterEncoding);
+			String value = this.contentType;
+			if (this.charset && !this.contentType.toLowerCase().contains(CHARSET_PREFIX)) {
+				value = value + ';' + CHARSET_PREFIX + this.characterEncoding;
 			}
-			doAddHeaderValue(HttpHeaders.CONTENT_TYPE, sb.toString(), true);
+			doAddHeaderValue(HttpHeaders.CONTENT_TYPE, value, true);
 		}
 	}
 
@@ -193,7 +193,8 @@ public class MockHttpServletResponse implements HttpServletResponse {
 		Assert.state(this.writerAccessAllowed, "Writer access not allowed");
 		if (this.writer == null) {
 			Writer targetWriter = (this.characterEncoding != null ?
-					new OutputStreamWriter(this.content, this.characterEncoding) : new OutputStreamWriter(this.content));
+					new OutputStreamWriter(this.content, this.characterEncoding) :
+					new OutputStreamWriter(this.content));
 			this.writer = new ResponsePrintWriter(targetWriter);
 		}
 		return this.writer;